Touch screens can be generally categorized into resistive touch screens and capacitive touch screens.
Capacitive touch screens can be categorized according to touch signal detection technology as self-capacitive and mutual-capacitive touch screens.
FIG. 1 illustrates an equivalent circuit of a typical mutual-capacitive touch screen in the related art, and referring to FIG. 1, a mutual-capacitive touch screen is consisted of multiple driving lines (e.g., Y1-Y4) and multiple sensing lines (e.g., X1-X4) intersecting perpendicularly. There is a sub-pixel of the touch screen in the dotted box. Capacitance of an overlapping part between a driving line and a sensing line is invariable by an object touching the screen, but the capacitance of the overlapping part may output stable background noise or a direct current component to a preamplifier A. Mutual-capacitance Cm formed by a space edge electric field arising from a non-overlapping part between the driving line and the sensing line is influenced directly by the touch of the object from the outside.
Referring to FIG. 1, an operation principle of the mutual-capacitive touch screen can be summarized as follows: a driving signal at a specific frequency is input to one end of each of the multiple driving lines, and one end of each of the multiple sensing lines is connected to one of the preamplifiers A which receives and amplifies a sensing signal of the mutual-capacitance Cm. When a finger touches the surface of the touch screen, for example, at the location T illustrated in FIG. 1, a part of current flows into the finger, which is equivalent to a change in the mutual-capacitance Cm between the driving line and the sensing line, and the signal that can be received by the preamplifier A is attenuated. The specific touch location T of the finger can be detected by detecting the change in signal on the respective sensing lines.
As is apparent from FIG. 1, the driving signal is respectively transmitted to each driving line through a scan drive circuit, and the signal output from each sensing line is amplified and output by the preamplifier.
FIG. 2 is a schematic structural diagram of an electrode which can be used in the mutual-capacitive touch screen illustrated in FIG. 1. Referring to FIG. 2, each sensing line X and each driving line Y is connected to the outside through a lead line. With an increasing density of pixels, there are more and smaller sensing lines and driving lines, and consequently there are more lead lines which are concentrated on the perimeter of the touch screen, thus making it more difficult to make a narrow frame. Moreover with an increasing number of driving lines, the scan drive circuit has to scan by column, thus making it more complex to implement. Furthermore there are as many preamplifiers as sensing lines, thus making the circuit structurally bulky.